Hydrogel Network Research Articles

Green synthesis of multifunctional responsive hydrogel embedded with silver, based on xanthan gum, N-isopropylacrylamide, vinyl imidazole, and Luffa cylindrica for wound healing

In this study, a pH- and temperature-responsive smart hydrogel was developed by utilizing Xanthan Gum (XG), N-Isopropylacrylamide (NIPAM), Vinyl Imidazole (VI), and Luffa cylindrical (LC). Semi-interpenetrating polymer networks (semi-IPNs) were created using free radical polymerization with N,N′-methylenebisacrylamide (MBA) as the cross-linker and ammonium persulfate (APS) as the initiator. Silver nanoparticles (AgNPs) were synthesized within semi-IPN hydrogel network structures to impart antibacterial properties. Malva sylvestris (MS) aqueous leaf extract was used as a reducing and stabilizing agent for the green synthesis of the AgNPs. The semi-IPN hydrogels exhibited pH- and temperature-responsive swelling behavior, which also enabled the controlled release of the drug. After 11 h, the cumulative release reached approximately 73% at pH 7.2 and 87% at pH 8.3. Additionally, the sustained release mechanism of the Trimethoprim drug was described using the Korsmeyer-Peppas model and was governed by Fickian diffusion. The drug-loaded semi-IPN@Ag nanocomposite hydrogel has demonstrated effective antibacterial activity against various Gram-negative and Gram-positive bacteria, indicating its promising potential as a wound dressing material for reducing infection risk.

Resolving dynamic and static characteristics of the fouling by alginate in membrane distillation via optical coherence tomography

In an effort to improve the efficiency of membrane distillation (MD) for recovering water from a high salinity feed, recent studies paid special attention to the effects of fouling by alginate, which is an anionic polysaccharide ubiquitously involved in marine sources. However, it is technically challenging to in-situ characterize the gel layer with a relatively low degree of optical visibility. Therefore, a particle-assisted strategy was proposed by this study to improve the characterization based on optical coherence tomography (OCT) and thereby resolve both the dynamic (i.e., relating to the spatiotemporal evolution) and static (i.e., relating to the morphological properties) characteristics for developing a gel layer in the MD process with an alginate-containing feed. When confirming the effectiveness of employing differently sized polystyrene microbeads as the tracer combined with alginate aggregates and the detector transferred into the network of hydrogel, all the characterization results reveal that the alginate aggregates could be deposited in a heterogeneous way to form a steady structure composed of a static layer (∼150 μm) and a dynamic layer (∼50 μm); ∼25% to ∼30% of the cross-sectional area could be dominated by submicron- and micron-sized fluid channels in the static layer. This study not only provides deeper insights into the fouling by alginate in MD, but also broadens the spectrum of OCT-based characterization.

Bacteria encapsulation into polyethylene glycol hydrogels using Michael-type addition reactions

AbstractHydrogel materials can be used to integrate bacteria cells into biohybrid systems. Here, we investigate the use of polyethylene glycol-based hydrogels that employ different Michael-type addition crosslinking chemistries, including thiol-acrylate, thiol-vinyl sulfone, and thiol-maleimide click reactions, for covalent hydrogel network formation and bacteria encapsulation. All crosslinking chemistries generated hydrogels that provided stable encapsulation and culture of Bacillus subtilis; however, significant differences in cell viability and cell morphology after encapsulation were identified. Thiol-acrylate hydrogels provided the highest cell viability and favored encapsulation of single cells, while thiol-maleimide hydrogels had the lowest cell viability and favored encapsulation of larger aggregates. These findings demonstrate the impact of crosslinking strategies for encapsulation of microorganisms into hydrogel networks and suggest that thiol-acrylate chemistries are favorable for many applications. Graphical abstract

Controlled stiffness and diffusivity of poly(ethylene glycol) hydrogel formed with cellulose-nanofiber framework

Hydrogels composed of polymer networks are widely used in industry and scientific research for high water retention and unique mechanical properties. Nevertheless, in ordinary hydrogel formation, the trade-off relationship between stiffness and mesh size remains a crucial consideration for practical applications. This study describes a facile approach to controlling hydrogel stiffness and mesh size by hybridizing poly(ethylene glycol) diacrylate (PEGDA) and methacrylated TEMPO-oxidized cellulose nanofibers (T-CNFMA). After disintegrating T-CNF by ultrasonication, T-CNFMA was synthesized resulting in a degree of substitution of 2.04 mmol/g. Incorporation of T-CNFMA in the PEGDA network allowed for independent control of hydrogel stiffness and mesh size by reinforcing the whole hydrogel network as a framework. Consequently, the swelling ratio and shear modulus could be manipulated by controlling the PEGDA/T-CNFMA ratio. Structural analyses revealed that an increase in the T-CNFMA content in the presence of a low amount of PEGDA resulted in a large mesh size with a constant stiffness. The diffusivity test was also consistent with the properties of the hydrogels. This result indicates that the incorporation of T-CNF in hydrogel network is useful to control the physical property of the hydrogel, especially for varying mesh size, regardless of stiffness alteration.

Simultaneous processing of both handheld biomixing and biowriting of kombucha cultured pre-crosslinked nanocellulose bioink for regeneration of irregular and multi-layered tissue defects

The nanocellulosic pellicle derived from the symbiotic culture of bacteria and yeast (Kombucha SCOBY) is an important biomaterial for 3D bioprinting in tissue engineering. However, this nanocellulosic hydrogel has a highly entangled gel network. This needs to be partially modified to improve its processability and extrusion ability for its applications in the 3D bioprinting area. To control its mechanical and biological properties for direct 3D bioprinting applications, uniform reinforcement of nanocellulose-interacting polymers and nanoparticles in such a prefabricated gel network is essential. In this study, the hydrogel network is partially hydrolyzed with organic acid and subsequently transformed into a 3D bioprintable polyelectrolyte complex with chitosan and kaolin nanoparticles without any chemical crosslinker using a handheld 3D bioprinter. This handheld bioprinter ensures homogeneity in both biomixing and bioprinting of chitosan and kaolin within the modified nanocellulose network for multi-layered bioprinted scaffolds through an extensional shear mechanism. The biomixing simulation, mechanical (static, dynamic, and cyclic), 3D bioprinting, and cellular studies confirm the homogeneous biomixing of kaolin nanoparticles and live cells in this nanocellulose-chitosan polyelectrolyte hydrogel. The combination of SCOBY-derived nanocellulose-chitosan bioink with kaolin nanoparticles and a screw-driven handheld extrusion bioprinter demonstrates a promising platform for layer-by-layer regeneration of complex tissues with homogeneous cell/particle distribution with high cell viability.

Preparation, Swelling, and Drug Release Studies of Chitosan-based Hydrogels for Controlled Delivery of Buspirone Hydrochloride.

Buspirone is used for the management of depression and anxiety disorders. Due to its short half-life and low bioavailability, it requires multiple daily doses and is associated with some side effects. This study aimed to develop chitosan-based hydrogels as drug-controlled release carriers. The objective of this study is to prepare chitosan-based hydrogels as controlled release carriers in order to overcome the side effects of buspirone HCl and improve patients' compliance and their life quality. Polymer chitosan was polymerized with two monomers, acrylic acid and itaconic acid, to synthesize pH-sensitive hydrogel. The Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) analysis were performed to confirm the structure formation and thermal stability. Water penetration capability and loading of the drug were performed by porosity and drug loading studies. The swelling and dissolution tests were performed to analyze the pH-sensitive nature of the developed hydrogels. FTIR, TGA, and DSC demonstrated that the chitosan-based hydrogels were successfully prepared. An increase in water penetration and drug loading into the hydrogel network was seen with the high incorporation of chitosan, acrylic acid, and itaconic acid. The swelling and dissolution studies revealed that prepared hydrogel offered the greatest swelling and drug release at a high pH of 7.4. The swelling and drug release from the hydrogel were affected by the concentrations of the incorporated contents. A controlled release of the drug was achieved by using chitosan-based hydrogel as a delivery carrier compared to commercial tablets of buspirone. The results showed that the developed chitosan-based hydrogel can be considered one of the most suitable drug carrier systems for the controlled delivery of buspirone.

Intelligent microneedle patch based on functionalized alginate and chitosan for long-term self-regulated insulin delivery

Severely diabetic patients need insulin input to maintain the body's glycemic balance. However, traditional injection methods are often associated with poor adherence and an increased risk of hypoglycemia. Microneedle technology offers a promising solution by minimizing pain and trauma during insulin administration. Nonetheless, achieving prolonged glycemic control by microneedle with high insulin loading remains a significant challenge. Herein, we introduce an innovative microneedle patch that draws inspiration from the elegant light-induced blooming of water lily petals. The patch features a glucose-responsive hydrogel network crafted from two modified polysaccharide polymers, which enables the delivery of long-acting insulin without depending on glucose oxidase. By incorporating phenylboronic acid-modified sodium alginate, quaternary ammonium chitosan, and polyvinyl alcohol into a hydrogel matrix, we have created a microneedle system that harbors dynamic borate ester linkages and electrostatic attractions, resulting in heightened sensitivity to blood glucose levels. The electrostatic interaction acts as a relatively stable crosslinking point, balancing the dynamic reproducibility response based on the borate ester bond. This self-adaptive hydrogel can regulate insulin-controlled release by responding to changes in glucose concentration. Herein, we achieved massive insulin loading (20 IU) with long lasting glycaemic control (48 h) in a single treatment of diabetic SD rats.

Metal welding-inspired phase change self-healing strategy applied to high-modulus hydrogel composites

The self-healing efficiencies of polymers are inversely proportional to their modulus, as the recovery of the polymer network heavily relies on the mobility of polymer chains. Therefore, reinvigorated by the metal welding, we have developed S-PAM-SA-x supercooling hydrogels, consisting of polyacrylamide hydrogel networks and inorganic CH3COONa·3H2O phase change materials. Subsequently, rigid self-healing H-PAM-SA-x composites were achieved via self-actuated crystallization-related phase change from the supersaturated hydrogels, resulting in a significant enhancement in mechanical properties. Notably, the Young’s modulus experienced an astonishing increase from 0.07 to 387.1 MPa. The H-PAM-SA-130 % composites demonstrated satisfactory self-healing performance based on the phase change of melting and crystallization, as the dominant mechanical carrier was found to be the crystal lattice rather than the PAM network. Leveraging the reversible nature of melting and crystallization, the same position can undergo multiple healing cycles without compromising self-healing efficiencies. Moreover, this distinctive dynamic phase change process significantly expands the range of functional applications, encompassing self-healing, adhesion, and patterns’ replication among others.

Spectroscopic and Thermal Characterisation of Interpenetrating Hydrogel Networks (IHNs) Based on Polymethacrylates and Pluronics, and Their Physicochemical Stability under Aqueous Conditions

This study describes the physicochemical characterisation of interpenetrating hydrogel networks (IHNs) composed of either poly(hydroxyethylmethacrylate, p(HEMA)) or poly(methacrylic acid, p(MAA)), and Pluronic block copolymers (grades F127, P123 and L121). IHNs were prepared by mixing the acrylate monomer with Pluronic block copolymers followed by free radical polymerisation. p(HEMA)–Pluronic blends were immiscible, evident from a lack of interaction between the two components (Raman spectroscopy) and the presence of the glass transitions (differential scanning calorimetry, DSC) of the two components. Conversely, IHNs of p(MAA) and each Pluronic were miscible, displaying a single glass transition and secondary bonding between the carbonyl group of p(MAA) and the ether groups in the Pluronic block copolymers (Raman and ATR-FTIR spectroscopy). The effect of storage of the IHNs in Tris buffer on the physical state of each Pluronic and on the loss of Pluronic from the IHNs were studied using DSC and gravimetric analysis, respectively. Pluronic loss from the IHNs was dependent on the grade of Pluronic, time of immersion in Tris buffer, and the nature of the IHN (p(HEMA) or p(MAA)). At equilibrium, the loss was greater from p(HEMA) than from p(MAA) IHNs, whereas increasing ratio of poly(propylene oxide) to poly(ethylene oxide) decreased Pluronic loss. The retention of each Pluronic grade was shown to be primarily due to its micellization; however, hydrogen bonding between Pluronic and p(MAA) (but not p(HEMA)) IHNs contributed to their retention.

Fracture-driven power amplification in a hydrogel launcher.

Robotic tasks that require robust propulsion abilities such as jumping, ejecting or catapulting require power-amplification strategies where kinetic energy is generated from pre-stored energy. Here we report an engineered accumulated strain energy-fracture power-amplification method that is inspired by the pressurized fluidic squirting mechanism of Ecballium elaterium (squirting cucumber plants). We realize a light-driven hydrogel launcher that harnesses fast liquid vapourization triggered by the photothermal response of an embedded graphene suspension. This vapourization leads to appreciable elastic energy storage within the surrounding hydrogel network, followed by rapid elastic energy release within 0.3 ms. These soft hydrogel robots achieve controlled launching at high velocity with a predictable trajectory. The accumulated strain energy-fracture method was used to create an artificial squirting cucumber that disperses artificial seeds over metres, which can further achieve smart seeding through an integrated radio-frequency identification chip. This power-amplification strategy provides a basis for propulsive motion to advance the capabilities of miniaturized soft robotic systems.

Influence of TEMPO on preparation of softwood nanofibrils and their hydrogel network properties

From an economic and environmental perspective, the use of less chemicals in the production of cellulose nanofibrils (CNFs) is advantageous. In this study, we investigated the oxidation (TEMPO/NaClO2/NaClO, pH 6.8) of softwood (SW) particles with varying amounts of TEMPO (16, 8 or 0 mg g−1 of wood). Following, TEMPO-oxidized SW nanofibrils (TO-SWNFs) were obtained by nanofibrillation and their size, morphology, and crystallite size were assessed. Hydrogel networks of TO-SWNFs were prepared and mechanical properties were measured in dH2O and phosphate buffered saline (PBS) to compare their performance for possible biomedical applications such as wound dressings. The results reveal that the presence of TEMPO is of importance for TO-SWNF network properties, presenting higher eq. H2O absorption (≈2500 %) and elongation at break (≈10 %) with good wet strength (≈180 kPa). In addition, a decrease in use of TEMPO catalyst from 16 to 8 mg g−1 of wood is possible, without detrimental effects on hydrogel network properties (dH2O absorption ≈ 2000 %, elongation at break ≈ 13 %, wet strength ≈ 190 kPa) related to applications as wound dressings.

Ionic Hydrogel-Based Moisture Electric Generators for Underwater Electronics.

Ubiquitous moisture is of particular interest for sustainable power generation and self-powered electronics. However, current moisture electric generators (MEGs) can only harvest moisture energy in the air, which tremendously limits the energy harvesting efficiency and practical application scenarios. Herein, the operationality of MEG from air to underwater environment, through a sandwiched engineered-hydrogel device with an additional waterproof breathable membrane layer allowing water vapor exchange while preventing liquid water penetration, is expanded. Underwater environment, the device can spontaneously deliver a voltage of 0.55V and a current density of 130µAcm-2 due to the efficient ion separation assisted by negative ions confinement in hydrogel networks. The output can be maintained even under harsh underwater environment with 10% salt concentration, 1ms-1 disturbing flow, as well as >40kPa hydraulic pressure. The engineered hydrogel used for MEG also exhibits excellent self-healing ability, flexibility, and biocompatibility. As the first demonstration of practical applications in self-powered underwater electronics, the MEG device is successfully powering a wireless emitter for remote communication in water. This new type of MEG offers an innovative route for harvesting moisture energy underwater and holds promise in the creation of a new range of innovative electronic devices for marine Internet-of-Things.

Photochemical Control of Network Topology in PEG Hydrogels.

Hydrogels are often synthesized through photoinitiated step-, chain-, and mixed-mode polymerizations, generating diverse network topologies and resultant material properties that depend on the underlying network connectivity. While many photocrosslinking reactions are available, few afford controllable connectivity of the hydrogel network. Herein, a versatile photochemical strategy is introduced for tuning the structure of poly(ethylene glycol) (PEG) hydrogels using macromolecular monomers functionalized with maleimide and styrene moieties. Hydrogels are prepared along a gradient of topologies by varying the ratio of step-growth (maleimide dimerization) to chain-growth (maleimide-styrene alternating copolymerization) network-forming reactions. The initial PEG content and final network physical properties (e.g., modulus, swelling, diffusivity) are tailored in an independent manner, highlighting configurable gel mechanics and reactivity. These photochemical reactions allow high-fidelity photopatterning and 3D printing and are compatible with 2D and 3D cell culture. Ultimately, this photopolymer chemistry allows facile control over network connectivity to achieve adjustable material properties for broad applications.

Sliding on Slide-Ring Gels

Recent investigations have pointed to physical entanglements that greatly outnumber chemical crosslinks as key sources of energy dissipation and low friction in hydrogel networks. Slide-ring gels are an emerging class of hydrogels described by their mobile crosslinks, which are formed by rings topologically constrained to slide along linear polymer chains within the network. These materials have enjoyed decades of study by polymer chemists but have been underexplored by the tribology community. In this work, we synthesized a pseudo-rotaxane crosslinker from poly(ethylene glycol) diacrylate (PEG-diacrylate) and α-cyclodextrin-acrylate followed by hydrogel networks by connecting the sliding crosslinks with polyacrylamide chains. The mechanical and tribological properties of slide-ring hydrogels were investigated using a custom-built microtribometer. Slide-ring hydrogels exhibit unique behavior compared to conventional covalently crosslinked polyacrylamide hydrogels and offer a vast design space for future investigations.Graphical

Myelin Sheath-Inspired Hydrogel Electrode for Artificial Skin and Physiological Monitoring.

Significant advancements in hydrogel-based epidermal electrodes have been made in recent years. However, inherent limitations, such as adaptability, adhesion, and conductivity, have presented challenges, thereby limiting the sensitivity, signal-to-noise ratio (SNR), and stability of the physiological-electrode interface. In this study, we propose the concept of myelin sheath-inspired hydrogel epidermal electronics by incorporating numerous interpenetrating core-sheath-structured conductive nanofibers within a physically cross-linked polyelectrolyte network. Poly(3,4-ethylenedioxythiophene)-coated sulfonated cellulose nanofibers (PEDOT:SCNFs) are synthesized through a simple solvent-catalyzed sulfonation process, followed by oxidative self-polymerization and ionic liquid (IL) shielding steps, achieving a low electrochemical impedance of 42 Ω. The physical associations within the composite hydrogel network include complexation, electrostatic forces, hydrogen bonding, π-π stacking, hydrophobic interaction, and weak entanglements. These properties confer the hydrogel with high stretchability (770%), superconformability, self-adhesion (28 kPa on pigskin), and self-healing capabilities. By simulating the saltatory propagation effect of the nodes of Ranvier in the nervous system, the biomimetic hydrogel establishes high-fidelity epidermal electronic interfaces, offering benefits such as low interfacial contact impedance, significantly increased SNR (30 dB), as well as large-scale sensor array integration. The advanced biomimetic hydrogel holds tremendous potential for applications in electronic skin (e-skin), human-machine interfaces (HMIs), and healthcare assessment devices.

Supercooling-Driven Homogenization and Strengthening of Hydrogel Networks.

By leveraging principles from metal grain refinement, we introduce a transformative technique for fabricating poly(vinyl alcohol) (PVA) hydrogels via supercooling-coupled wet annealing, significantly enhancing their mechanical robustness and isotropy while maintaining their exceptionally high water content. Our methodology involves the dissolving PVA in water at elevated temperatures, mirroring the homogeneity achieved with a molten metal, in order to ensure a uniform distribution of polymer chains. This uniformity facilitates a rapid cooling phase that generates ultrafine ice crystals, setting the stage for a crucial solvent exchange with ethylene glycol (EG). The EG-mediated supercooling technique ensures the polymer homogeneity and structure integrity and induces the PVA chains to aggregate and form high-density hydrogen bonds, leading to a uniformly distributed, interconnected PVA network with high crystallinity. The process is further strengthened by EG-enabled wet annealing, which promotes the formation of densely packed crystalline domains within the polymer network. This rigorous process yields PVA hydrogels with superior mechanical properties, including a tensile strength of 13.65 MPa and a fracture toughness of 35.39 MJ m-3, alongside remarkable water content nearing 80%. These advances not only surpass the capabilities of conventional hydrogels but also broaden their application potential, highlighting the innovative integration of supercooling principles in polymer science.

A Bio-Inspired Multifunctional Hydrogel Network with Toughly Interfacial Chemistry for Dendrite-Free Flexible Zinc Ion Battery.

Flexible and high-performance aqueous zinc-ion batteries (ZIBs), coupled with low cost and safe, are considered as one of the most promising energy storage candidates for wearable electronics. Hydrogel electrolytes present a compelling alternative to liquid electrolytes due to their remarkable flexibility and clear advantages in mitigating parasitic side reactions. However, hydrogel electrolytes suffer from poor mechanical properties and interfacial chemistry, which limits them to suppressed performance levels in flexible ZIBs, especially under harsh mechanical strains. Herein, a bio-inspired multifunctional hydrogel electrolyte network (polyacrylamide (PAM)/trehalose) with improved mechanical and adhesive properties was developed via a simple trehalose network-repairing strategy to stabilize the interfacial chemistry for dendrite-free and long-life flexible ZIBs. As a result, the trehalose-modified PAM hydrogel exhibits a superior strength and stretchability up to 100 kPa and 5338 %, respectively, as well as strong adhesive properties to various substrates. Also, the PAM/trehalose hydrogel electrolyte provides superior anti-corrosion capability for Zn anode and regulates Zn nucleation/growth, resulting in achieving a high Coulombic efficiency of 98.8 %, and long-term stability over 2400 h. Importantly, the flexible Zn//MnO2 pouch cell exhibits excellent cycling performance under different bending conditions, which offers a great potential in flexible energy-related applications and beyond.

The effect of swelling/deswelling cycles on the mechanical behaviors of the polyacrylamide hydrogels

In practical applications, hydrogels experience swelling or deswelling in response to external stimuli, showcasing large deformation, tunable mechanical properties, and excellent biocompatibility. Previous studies focused on the effect of individual swelling or deswelling on the mechanical behaviors of hydrogels, neglecting the combined effects of both processes. The underlying mechanism of how the combined processes of swelling and deswelling affect the mechanical behaviors of hydrogels has not been systematically explored. To address this gap, polyacrylamide hydrogels with diverse initial compositions are prepared and subjected to controlled swelling-deswelling or deswelling-swelling cycles to achieve the same water content state. The mechanical properties of the hydrogel samples exposed to these cycles, including shear modulus, stretchability, Mullins effect, and fracture toughness, are experimentally evaluated and compared with those of as-prepared hydrogel samples without undergoing such cycles. Our findings reveal a significant reduction in stretchability, the Mullins effect, and fracture toughness of hydrogels exposed to either cycle. The extent of these reductions varies depending on the initial compositions of the hydrogels. This reduction in properties is primarily attributed to the rearrangement of hydrogel networks during these cycles, which becomes noticeable in hydrogels with network inhomogeneity. We also found that although the shear modulus of hydrogels varies after swelling-deswelling or deswelling-swelling cycles, it remains at relatively consistent levels compared to the as-prepared hydrogel. These findings suggest that the mechanical properties of hydrogels can be adjusted by optimizing the initial compositions and regulating the swelling-deswelling processing method. By studying the effects of swelling/deswelling cycles on the mechanical properties of hydrogels, we provide valuable insights for the application of hydrogels under dynamic environmental changes.

A self-gelling alginate/chitosan based powder containing bioactive nanoparticles for non-compressible bleeding control and promoting wound healing

The challenge remains in developing hemostatic dressings that can fulfill both hemostatic and repair functions to meet clinical demands worldwide. Herein, the biodegradable powders composed of benzeneboronic acid-modified sodium alginate/catechol-modified quaternized chitosan hydrogel (SBQCC) networks and bioactive cerium oxide nanoparticles (CNPs), were prepared for hemostasis and promoting wound healing. The SBQCC/CNPs powders had good self-gelation ability, water absorption ratio, tissue adhesiveness and biocompatibility. The SBQCC/CNPs powders could not only rapidly absorb a large amount of blood to concentrate coagulation factors when applied on bleeding wounds, but also formed an adhesive hydrogel physical barrier to control bleeding in situ. Meanwhile, the aggregation and activation of red blood cells and platelets induced by the SBQCC/CNPs powders can initiate the forming of internal blood clot with fibrin to further enhance the hemostatic effect. The SBQCC/CNPs powders demonstrated excellent hemostatic performance in non-compressible rat tail vein bleeding and rabbit liver bleeding models. In addition, SBQCC/CNPs powder-derived hydrogels had antibacterial activity and multiple biological activities, including antioxidant, anti-inflammatory and promoting angiogenesis for accelerating wound healing. Therefore, the SBQCC/CNPs powders can accelerate wound healing while achieving effective hemostasis, which will be a promising hemostatic dressing.

Hagfish-inspired hydrogel for root caries: A multifunctional approach including immediate protection, antimicrobial phototherapy, and remineralization

Root caries is the main cause of oral pain and tooth loss in the elderly. Protecting root lesions from environmental disturbances, resisting pathogens, and facilitating remineralization over time are essential for addressing root caries, but are challenging due to the irregular root surface and the complex oral environment. Hagfish secretes slime when facing danger, which converts into gels upon contact with seawater, suffocating the predators. Inspired by hagfish's defense mechanism, a fluid-hydrogel conversion strategy is proposed to establish a mechanical self-regulating multifunctional platform for root caries treatment. The fluid system (silk fibroin-tannic acid-black phosphorene-urea, ST-BP-U), in which urea disrupts the hydrogen bonds between silk fibroin and tannic acid, can easily spread on the irregular root surface and permeate into dentinal tubules. Upon contact with the surrounding water, urea diffuses, prompting the hydrogel re-formation and creating intimate attachments with micromechanical inlay locks. Meanwhile, BP increases the crosslinking of the re-formed hydrogel network, resulting in reinforced cohesion for robust wet adhesion to the tooth root. This process establishes a structured platform for effective antimicrobial phototherapy and dentin remineralization promotion. This water-responsive fluid-hydrogel conversion system adapts to the irregular root surface in the dynamic wet environment, holding promise for addressing root caries. Statement of significanceRoot caries bring a heavy burden to the aging society, but the irregular root surface and dynamic moist oral environment always hinder non-surgical therapeutic effects. Here, we propose a water-responsive fluid-hydrogel conversion strategy aimed at mechanical self-regulation on the irregular and wet root interface to construct a functional structural platform. The liquid system (ST-BP-U) that prebreak intermolecular hydrogen bonds can easily spread on irregular surfaces and dentin tubules. When encountering water, hydrogen bonds re-form, and BP increases the crosslinking of the hydrogel formed in situ. Based on this firm wet-adhesion platform, it provides powerful phototherapy effects and promotes dentin remineralization. This fluid-hydrogel conversion system turns the disadvantages of wet environment into advantages, offering a promising strategy for root caries.